According to the American Academy of Orthopedic Surgeons, about 250,000 spinal fusion surgeries are performed every year, mostly on adults between the ages of 45 to 64. Spinal fusion is a process by which two or more of the vertebrae that make up the spinal column are fused together with bone grafts and internal devices (such as rods) that heal into a single solid bone. Spinal fusion can eliminate unnatural motion between the vertebrae and, in turn, reduce pressure on nerve endings. In addition, spinal fusion can be used to treat, for example, injuries to spinal vertebrae caused by trauma; protrusion and degeneration of the cushioning disc between vertebrae (sometimes called slipped disc or herniated disc); abnormal curvatures (such as scoliosis or kyphosis); and weak or unstable spine caused by infections or tumors.
Individuals who suffer degenerative disc disease, natural spine deformations, a herniated disc, spine injuries or other spine disorders may require surgery on the affected region to relieve the individual from pain and prevent further injury to the spine and nerves. Spinal surgery may involve removal of damaged joint tissue, insertion of a tissue implant and/or fixation of two or more adjacent vertebral bodies. In some instances a medical implant is also inserted, such as a fusion cage. The surgical procedure will vary depending on the nature and extent of the injury. Generally, there are five main types of lumbar fusion, including: posterior lumbar fusion (“PLF”), posterior lumbar interbody fusion (“PLIF”), anterior lumbar interbody fusion (“ALIF”), circumferential 360 fusion, and transforaminal lumbar interbody fusion (“TLIF”). More recently, direct lateral interbody fusion (“D-LIF”) has become available. A posterior approach is one that accesses the surgical site from the patient's back, an anterior approach is one that accesses the surgical site from the patient's front or chest, and a direct lateral approach is on that accesses the surgical site from the patient's side. There are similar approaches for fusion in the interbody or cervical spine regions. For a general background on some of these procedures and the tools and apparatus used in certain procedures, see U.S. Prov. Pat. Appl. No. 61/120,260 filed on Dec. 5, 2008, the entire disclosure of which is incorporated by reference in its entirety. In addition, further background on procedures and tools and apparatus used in spinal procedures is found in U.S. patent application Ser. No. 12/632,720 filed on Dec. 7, 2009, the entire disclosure of which is incorporated by reference in its entirety.
Vertebrectomy, or the removal or excision of a vertebra, is another type of spinal surgery that may be necessary to alleviate pain and/or correct spinal defects, such as when disk material above and below a particular vertebra protrudes from the spine and contacts the spinal cord. Once the problematic vertebra is removed, a specialized fusion cage (also called a vertebrectomy cage) may be inserted into its place to restore structural continuity to the spine.
Some disadvantages of traditional methods of spinal surgery include, for example, the pain associated with the procedure, the length of the procedure, the complexity of implements used to carry out the procedure, the prolonged hospitalization required to manage pain, the risk of infection due to the invasive nature of the procedure, and the possible requirement of a second procedure to harvest autograft bone from the iliac crest or other suitable site on the patient for generating the required quantity of cancellous and/or cortical bone.
A variety of semisolid bone graft materials are available on the market which ostensibly increase spinal fusion rates without the morbidity of autograft bone harvest. Each of the manufacturers espouses their product as the most advantageous for healing. These products all have similar handling characteristics and the literature reveals that they have similar healing prospects. They come in a syringe and it is up to the surgeon to apply the selected material to the target site. The most common site for application is to the disk space after it has been prepared to a bleeding bed and ready to accept a cage and/or the grafting material. This represents a long and narrow channel even in open procedures. The surgeon is left to his own devices as to how to get the graft from its container to the active site. The devices which have been used have included a “caulking gun” construct and a variety of barrel shaft with a plunger design.
Bone graft typically includes crushed bone (cancellous and cortical), or a combination of these (and/or other natural materials), and may further comprise synthetic biocompatible materials. Bone graft of this type is intended to stimulate growth of healthy bone. As used herein, “bone graft” shall mean materials made up entirely of natural materials, entirely of synthetic biocompatible materials, or any combination of these materials. Bone graft often is provided by the supplier in a gel or slurry form, as opposed to a dry or granule form. Many companies provide various forms of bone graft in varying degrees of liquidity and viscosity, which may cause problems in certain prior art delivery devices in both prepackaged or packaged by the surgeon embodiments. In addition, the method of delivery of bone graft to a particular location varies depending on the form of the bone graft utilized.
Autogenous bone (bone from the patient) or allograft bone (bone from another individual) are the most commonly used materials to induce bone formation. Generally, small pieces of bone are placed into the space between the vertebrae to be fused. Sometimes larger solid pieces of bone are used to provide immediate structural support. Autogenous bone is generally considered superior at promoting fusion. However, this procedure requires extra surgery to remove bone from another area of the patient's body such as the pelvis or fibula. Thus, it has been reported that about 30 percent of patients have significant pain and tenderness at the graft harvest site, which may be prolonged, and in some cases outlast the back pain the procedure intended to correct. Similarly, allograft bone and other bone graft substitutes, although eliminating the need for a second surgery, have drawbacks in that they have yet to be proven as cost effective and efficacious substitutes for autogenous bone fusion.
An alternative to autogenous or allograft bone is the use of growth factors that promote bone formation. For example, studies have shown that the use of bone morphogenic proteins (“BMPs”) results in better overall fusion, less time in the operating room and, more importantly, fewer complications for patients because it eliminates the need for the second surgery. However, use of BMPs, although efficacious in promoting bone growth, can be prohibitively expensive.
Another alternative is the use of a genetically engineered version of a naturally occurring bone growth factor. This approach also has limitations. Specifically, surgeons have expressed concerns that genetically engineered BMPs can dramatically speed the growth of cancerous cells or cause non-cancerous cells to become more sinister. Another concern is unwanted bone creation. There is a chance that bone generated by genetically engineered BMPs could form over the delicate nerve endings in the spine or, worse, somewhere else in the body.
Regenerative medicine, which harnesses the ability of regenerative cells, e.g., stem cells (i.e., the unspecialized master cells of the body) to renew themselves indefinitely and develop into mature specialized cells, may be a means of circumventing the limitations of the prior-art techniques. Stem cells, i.e., both embryonic and adult stem cells, have been shown to possess the nascent capacity to become many, if not all, of the 200+ cell and tissue types of the body, including bone. Recently, adipose tissue has been shown to be a source of adult stem cells (See e.g. Zuk, Patricia Z. et al., “Multilineage Cells from Human Adipose Tissue: Implication for Cell-Based Therapies,” Tissue Engineering, April 2001, 7:211-28; Zuk, Patricia A. et al., “Human Adipose Tissue Is A Source Of Multipotent Stem Cells,” Molecular Biology of the Cell, 2002, 13:4279-4295). Adipose tissue (unlike marrow, skin, muscle, liver and brain) is comparably easy to harvest in relatively large amounts with low morbidity (See e.g. Commons, G. W., Halperin, B., and Chang, C. C. (2001) “Large-volume liposuction: a review of 631 consecutive cases over 12 years” Plast. Reconstr. Surg. 108, 1753-63; Katz, B. E., Bruck, M. C. and Coleman, W. P. 3 (2001b) “The benefits of powered liposuction versus traditional liposuction: a paired comparison analysis” Dermatol. Surg. 27, 863-7). Accordingly, given the limitations of the prior art spinal fusion techniques, there exists a need for a device that incorporates regenerative cells, e.g., stem cells that posses the ability to induce bone formation.
Many different methods and approaches have been attempted to induce bone formation or to promote spinal fusion. The traditional devices for inserting bone graft impair the surgeon's visualization of the operative site, which can lead to imprecise insertion of bone graft and possible harm to the patient. The caulking gun and the collection of large barrel/plunger designs typically present components at the top of their structure which block the view of the surgical site. The surgeon must then resort to applying pressure to the surgical site to approximate the location of the device's delivery area. Such rough maneuvering can result in imprecise placement of bone graft, and in some cases, rupture of the surgical area by penetrating the annulus and entering the abdominal cavity. Also, in some surgical procedures, the devices for inserting bone graft material are applied within a cannula inserted or placed in the surgical area, further limiting the size and/or profile of the bone graft insertion device. When a cannula is involved, some traditional devices such as the large barrel/plunger designs and/or the chalking gun designs simply cannot be used as they cannot be inserted within the cannula.
Traditional devices for inserting bone graft deliver the bone graft material at the bottom of the delivery device along the device's longitudinal axis. Such a delivery method causes the bone grafting material to become impacted at the bottom of the delivery device, and promotes risk of rupture of the surgical area by penetrating the annulus and entering the abdominal cavity. Further, traditional devices that deliver bone graft material along their longitudinal axis may cause rupture of the surgical area or harm to the patient because of the ensuing pressure imparted by the ejected bone graft material from the longitudinal axis of the device.
As mentioned, the method of delivery of bone graft to a particular location varies depending on the form of the bone graft utilized. For example, in the case of slurry type bone graft, various dispensing devices have been developed having applicators designed to accommodate this type of bone graft. One such device is disclosed by U.S. Pat. No. 5,925,051 issued to Mikhail on Jul. 20, 1999 (“Mikhail”). Mikhail provides a caulking gun type dispenser for introducing bone graft in an enlarged bone (e.g. femoral) cavity. The device preferably includes a barrel pre-loaded with bone graft and a cannulated ejector positioned over a multi-section guide wire. This arrangement purports to accomplish both ejecting bone graft from the barrel and compacting the bone graft material while being guided on the guide wire. Mikhail, however, is designed solely for use with slurry-type bone graft, and does not accommodate bone graft in granule form, which often varies in size among granules and does not have the same “flow” or viscosity characteristics as slurry-type bone graft. Thus, the applicator of Mikhail is insufficient for introducing most bone graft to a surgical site in a patient.
U.S. Pat. No. 6,019,765 issued to Thornhill et al. on Feb. 1, 2000 (“Thornhill”) also teaches a bone graft delivery device. The bone graft device applicator of Thornhill is used to apply bone graft to an artificial joint without having to remove a previously implanted prosthesis component. The applicator device includes a hollow tube with an actuation mechanism for discharging the bone graft from the device via a nozzle coupled to a distal end of the tube. The bone graft delivery device of Thornhill may include various components for loading the device with the bone graft, and may further include a plurality of nozzles each having a geometry suited for a particular application. Like Mikhail, the Thornhill delivery device is designed for use with bone slurry, and requires much custom instrumentation and different sized parts to achieve success in many bone graft delivery applications, which in turn increases the time to assemble and use the delivery device and may create further problems during the surgical operation.
U.S. Pat. No. 5,697,932 issued to Smith et al. on Dec. 16, 1997 (“Smith”) discloses yet another bone graft delivery system and method. In Smith, a hollow tube of pre-loaded bone graft and a plunger are used to facilitate delivery of the bone graft to a bone graft receiving area. A positioning structure is provided on the plunger to maintain the plunger in a desirable position with respect to the hollow tube. Adjunct positioning means may also be provided to ensure that the plunger remains in the desirable position during the packing of bone graft into the bone graft receiving area. Like the devices of Thornhill and Mikhail, the device disclosed by Smith is clearly designed solely for slurry type bone graft, and does not provide an effective opening for receiving the desired amount of bone graft. Furthermore, the hollow tube shown by Smith is narrow and does not have a footing or other apparatus associated with the delivery device for preventing the device from penetrating, for example, the abdominal region of a patient, which may occur during tamping or packing of the bone graft. This in turn may cause serious injury to a patient if not controlled, and for these reasons the device of Smith is also insufficient for delivery of bone graft to a surgical site.
Traditional devices for inserting a fusion cage or other medical implants into a patient's spine or other surgical area are distinct and separate from traditional devices that deliver bone graft material to the surgical site. For example, once an implant has been positioned, then bone growth material is packed into the internal cavity of the fusion cage. Also, sometimes the process is reversed, i.e., the bone growth is inserted first, and then the implant. These bone growth inducing substances come into immediate contact with the bone from the vertebral bone structures which project into the internal cavity through the apertures. Two devices are thus traditionally used to insert bone graft material into a patient's spine and to position and insert a fusion cage. These devices thus necessitate a disc space preparation followed by introduction of the biologic materials necessary to induce fusion and, in a separate step, application of a structural interbody fusion cage.
The problems associated with separate administration of the biologic material bone graft material and the insertion of a fusion cage include applying the graft material in the path of the cage, restricting and limiting the biologic material dispersed within the disk space, and requiring that the fusion cage be pushed back into the same place that the fusion material delivery device was, which can lead to additional trauma to the delicate nerve structures.
Fusion cages provide a space for inserting a bone graft between adjacent portions of bone. Such cages are often made of titanium and are hollow, threaded, and porous in order to allow a bone graft contained within the interior of the cage of grow through the cage into adjacent vertebral bodies. Such cages are used to treat a variety of spinal disorders, including degenerative disc diseases such as Grade I or II spondylolistheses of the lumbar spine.
Surgically implantable intervertebral fusion cages are well known in the art and have been actively used to perform spinal fusion procedures for many years. Their use became popularized during the mid 1990's with the introduction of the BAK Device from the Zimmer Inc., a specific intervertebral fusion cage that has been implanted worldwide more than any other intervertebral fusion cage system. The BAK system is a fenestrated, threaded, cylindrical, titanium alloy device that is capable of being implanted into a patient as described above through an anterior or posterior approach, and is indicated for cervical and lumbar spinal surgery. The BAK system typifies a spinal fusion cage in that it is a highly fenestrated, hollow structure that will fit between two vertebrae at the location of the intervertebral disc.
Spinal fusion cages may be placed in front of the spine, a procedure known as anterior lumbar interbody fusion, or ALIF, or placed in back of the spine. The cages are generally inserted through a traditional open operation, though laparoscopic or percutaneous insertion techniques may also be used. Cages may also be placed through a posterior lumbar interbody fusion, or PLIF, technique, involving placement of the cage through a midline incision in the back, or through a direct lateral interbody fusion, or D-LIF, technique, involving placement of the cage through an incision in the side.
A typical procedure for inserting a common threaded and impacted fusion cage is as follows. First, the disc space between two vertebrae of the lumbar spine is opened using a wedge or other device on a first side of the vertebrae. The disk space is then prepared to receive a fusion cage. Conventionally, a threaded cage is inserted into the bore and the wedge is removed. A disk space at the first side of the vertebrae is then prepared, and a second threaded fusion cage inserted into the bore. Alternatively, the disk space between adjacent vertebrae may simply be cleared and a cage inserted therein. Often, only one cage is inserted obliquely into the disk space. Use of a threaded cage may be foregone in favor of a rectangular or pellet-shaped cage that is simply inserted into the disk space. Lastly, bone graft material may be inserted into the surgical area using separate tools and devices.
U.S. Pat. No. 4,743,256 issued to Brantigan (“Brantigan”) discloses a traditional spinal back surgical method involving the implantation of a spinal fusion cage. The cage surfaces are shaped to fit within prepared endplates of the vertebrae to integrate the implant with the vertebrae and to provide a permanent load-bearing strut for maintaining the disc space. Brantigan teaches that these cages typically consist of a homogeneous nonresorbable material such as carbon-reinforced polymers such as polyether ether ketone (PEEK) or polyether ketone ether ketone ketone (“PEKEKK”). Although these cages have demonstrated an ability to facilitate fusion, a sufficient fusion is sometimes not achieved between the bone chips housed within the cage and the vertebral endplates. In particular, achieving a complete fusion in the middle portion of the cage has been particularly problematic. As shown in FIG. 6 herein, the upper U and lower L surfaces of these cages C have large transverse pores P which facilitate bone ingrowth, and these pores lead to an inner void space IVS which houses bone graft (not shown) which facilitates the desired fusion. In any case, Brantigan teaches the separate process and procedure for the insertion of a fusion cage and the insertion of bone graft. Indeed, local bone graft harvested from the channel cuts into the vertebrae to receive the plug supplements the fusion.
U.S. Pat. Appl. 20070043442 of Abernathie et al. (“Abernathie”) discloses another traditional spinal back surgical method involving the implantation of a spinal fusion cage. Abernathie relates generally to an implantable device for promoting the fusion of adjacent bony structures, and a method of using the same. More specifically, Abernathie relates to an expandable fusion cage that may be inserted into an intervertebral space, and a method of using the same. Abernathie includes an aperture in the fusion cage to allow bone growth therethrough, as a separate procedure to the insertion of the fusion cage.
Traditional fusion cages are available in a variety of designs and composed of a variety of materials. The cages or plugs are commonly made of an inert metal substrate such as stainless steel, cobalt-chromium-molybdenum alloys, titanium or the like having a porous coating of metal particles of similar substrate metal, preferably titanium or the like as disclosed, for example, in the Robert M. Pilliar U.S. Pat. No. 3,855,638 issued Dec. 24, 1974 and U.S. Pat. No. 4,206,516 issued Jun. 10, 1980. These plugs may take the form of flat sided cubical or rectangular slabs, cylindrical rods, cruciform blocks, and the like.
U.S. Pat. No. 5,906,616 issued to Pavlov et al. (“Pavlov”) discloses a fusion cage of various cylindrical and conical shapes and a method of insertion. Like Brantigan, Pavlov teaches the separate process and procedure for the insertion of a fusion cage and the insertion of bone graft. U.S. Pat. No. 5,702,449 (“McKay”) discloses a spinal implant comprising a cage made of a porous biocompatible material reinforced by an outer sleeve made of a second material which is relatively stronger under the compressive load of the spine than the biocompatible material. U.S. Pat. No. 6,569,201 issued to Moumene et al. (“Moumene”) teaches a bone fusion device having a structural bioresorbable layer disposed upon the outer surface of a non-resorbable support. As the bioresorbable structural layer resorbs over time, the load upon the bone graft housed within the non-resorbable support increases. Published PCT Application No. WO 99/08627 (“Gresser”) discloses a fully bioresorbable interbody fusion device, as well as homogeneous composite devices containing at least 25% resorbable materials. U.S. Pat. No. 7,867,277 issued to Tohmeh discloses a spinal fusion implant of bullet shaped end.
U.S. Pat. No. 7,846,210 issued to Perez-Cruet et al. (“Perez-Cruet”) discloses an interbody device assembly consisting of a fusion device and an insertion device. The insertion device positions the fusion device between two vertebrae, provides bone graft material, and then detaches from the fusion device, leaving the fusion device in place to restore disc space height. However, the Perez-Cruet device is designed to receive bone graft material from its insertion device and distribute the material away from the fusion device. In most embodiments of the fusion device, a center plate is positioned immediately downstream of the received bone graft material and directs the bone graft to opposing sides of the fusion device. (See, for example, FIG. 20 depicting plate 308 directing bone graft material 392 along the exterior sides of the fusion device 302). As such, the Perez-Cruet fusion device is unlikely to completely fill the areas near of its fusion cage and deliver bone graft material to the surrounding bone graft site. Furthermore, none of the Perez-Cruet fusion device embodiments feature a defined interior space or a cage-style design. Indeed, the Perez-Cruet fusion device explicitly teaches away from a contained-interior, fusion-cage-style device, asserting that its fusion device fills all of the disc space as opposed to a cage design, which contains the bone material. Furthermore, the Perez-Cruet does not feature a distal tip that functions to precisely position the fusion device and stabilize the device during delivery of bone graft material.
U.S. Pat. No. 7,985,256 issued to Grotz et al. (“Grotz”) discloses an expandable spinal implant for insertion between opposed vertebral end plates. The implant is a cylinder block of slave cylinders; a central cavity between the cylinders receives bone graft material and pistons positioned within the cylinders provide a corrective bone engaging surface for expanding against a first vertebral end plate. The insertion tool used to place the spinal implant includes a handle and hollow interior for housing hydraulic control lines and a bone graft supply line. The Grotz system does not allow precise positioning or delivery of bone graft material without an implant and requires a complex and bulky insertion tool.
U.S. Pat. Appl. 2010/0198140 to Lawson (“Lawson”) discloses a tool comprising a cannula with an open slot at the distal end and a closed tip. Lawson's tool employs tamps to push bone aside and open up a void for filling; solid bone pellets are then rammed down the hollow interior of the cannula by a tamper and delivered to the surgical site. Lawson does not allow precise positioning or delivery of viscous bone graft material and has no capability to interconnect or integrate with an implant such as a bone graft fusion cage.
U.S. Pat. Appl. 2010/0262245 to Alfaro et al. (“Alfaro”) discloses a delivery system for an intervertebral spacer and a bone grafting material comprising a spacer disengagingly attached to a hollow handle. The handle comprises a chamber and bone grafting material-advancing means for introducing bone grafting material from the chamber into the spacer and the intervertebral spaces. The Alfaro system does not allow precise positioning or delivery of bone graft material through a distal tip that precisely positions the fusion device and stabilizes the device during delivery of bone graft material, and does not allow primarily lateral injection of bone graft fusion material.
The prior art bone graft delivery devices listed above typically must come pre-loaded with bone graft, or alternatively require constant loading (where permissible) in order to constantly have the desired supply of bone graft available. Moreover, these bone graft delivery devices generally cannot handle particulate bone graft of varying or irregular particulate size. Furthermore, the prior art devices for inserting a fusion cage or other medical implant into a patient's spine or other surgical area are commonly distinct and separate from traditional devices that deliver bone graft material to the surgical site. As such, two devices are traditionally used to insert bone graft material into a patient's spine and to position and insert a fusion cage. The problems associated with separate administration of the biologic material bone graft material and the insertion of a fusion cage include applying the graft material in the path of the cage, restricting and limiting the biologic material dispersed within the disk space, and requiring that the fusion cage be pushed back into the same place that the fusion material delivery device was, which can lead to additional trauma to the delicate nerve structures. These problems can be a great inconvenience, cause avoidable trauma to a patient and make these prior art devices unsuitable in many procedures.
Therefore, there is a long-felt need for an apparatus and method for near-simultaneous and integrated precision delivery of bone graft material during the placement of surgical cages or other medical implants in a patient's spine. The present invention solves these needs. The present invention allows biologic material to flow directly to the fusion cage and be dispersed within the disc space in a single step, and can precisely and simply deliver particulate bone graft of varying or irregular particulate size. Thus, the present invention allows application of bone graft material through a detachable fusion cage, eliminates otherwise restriction of the volume of biologic material that may be dispersed within the disk space, and eliminates the requirement that the fusion cage be pushed back into the same place that the fusion material delivery device was, which can lead to additional trauma to the delicate nerve structures.